This application claims the priority of German Patent Application No. 299 19 989.4 filed Nov. 15, 1999, the subject matter of which is incorporated herein by reference.
The invention relates to an optoelectronic arrangement for determining the height profile of an object with the aid of a range finder including a transmitter that emits light rays and a receiver that receives light rays. The arrangement further comprises a deflection unit for periodically deflecting the transmitting light rays and guiding them over the object surface, wherein the height profile of the object is determined in an evaluation unit based on the range values at the range finder output and the associated deflection angles for the transmitting light rays.
An optoelectronic arrangement of this type is known from German patent document 44 05 376 C1. This arrangement comprises a transmitter for emitting light rays, as well as a receiver for receiving light rays, which together form a range finder operating on the basis of the phase measuring principle. The transmitting light rays are deflected via a deflection unit, so that they sweep a monitoring range in a plane. For this, the deflection unit is provided with a rotating mirror, across which the transmitting light rays and the receiving light rays are guided. An angle transmitter is used to detect the position of the rotating mirror and thus the momentary deflection angle of the transmitting light rays. The position of objects in the monitoring range can be determined from the range values at the range finder output, as well as the output signals from the angle transmitter. In particular, it is also possible to detect the height profile of objects in the monitoring range by scanning their surfaces with the transmitting light rays.
In this arrangement, the deflection unit with rotating mirror represents a moving part with relatively large mass, which is a particular disadvantage if the arrangement is used on machines, for example in outdoor areas. Strong vibrations occur with machines of this type, which can be transmitted to the optoelectronic arrangement and can thus cause faulty measurements or even malfunctions or failures of the arrangement.
Furthermore, the transmitting and receiving light rays for this arrangement are guided coaxial over the rotating mirror. This is a particular advantage for detecting objects in the close-in area, especially those directly in front of the arrangement. However, if the arrangement is to be used outdoors for determining the contours of objects arranged at a longer distance to the arrangement, then the high sensitivity of the arrangement for the close-in range can be a disadvantage. In particular, this is the case if the arrangement is installed on a machine exposed to the development of dust in the surrounding area. In that case, the dust immediately in front of the arrangement will reflect back a portion of the transmitting light rays, thus leading to measuring value distortions during the distance measuring.
It is an object of the invention to realize an arrangement of the aforementioned type so that it is as insensitive as possible against interfering outside influences.
The above and other objects are accomplished in accordance with the invention by the provision of an optoelectronic arrangement for determining a height profile of an object, comprising: a range finder having an output and including a transmitter that emits light rays and a receiver that receives light rays; a deflection unit for periodically deflecting the transmitting light rays and guiding them over a surface of the object, the deflection unit including a transmitting optic arranged downstream of the transmitter and an actuator for periodically deflecting the transmitting light; a receiving optic arranged in front of the receiver and at a distance from the transmitting optic so that a beam axis of the transmitting light rays that penetrate the transmitting optic and a beam axis of receiving light rays that penetrate the receiving optic extend at a distance to each other; and an evaluation unit, coupled to the output of the range finder and the deflection unit, determining the height profile of the object from range values at the range finder output and associated deflection angles for the transmitting light rays.
The optoelectronic device according to the invention thus comprises a deflection unit which includes an actuator to periodically deflect a transmitting optic arranged downstream of the transmitter.
In addition, a receiving optic is arranged in front of the receiver, at a distance to the transmitting optic, so that the beam axes for the transmitting rays penetrating the transmitting optic and the receiving rays penetrating the receiving optic pass at a distance to each other.
One essential advantage of the arrangement according to the invention is that in order to deflect the transmitting light rays, the transmitting optic is deflected by means of the actuator. In the process, the transmitting optic performs a forced movement that is insensitive to vibrations of the arrangement.
Another advantage is that the transmitting light rays that are guided over the transmitting optic pass at a distance to the receiving light rays guided over the receiving optic. With a suitable selection of the basic distance between transmitting optic and receiving optic, the arrangement becomes insensitive to interfering influences in the close-in range, particularly against dust developing in the area immediately surrounding the optoelectronic arrangement. This is based on the fact that transmitting light rays beamed back from the close-in range do not impinge on the receiver, owing to the distance between transmitting optic and receiving optic, and thus do not cause faulty measurements there.